Of the enormous quantity of synthetic polymer compositions produced, about eighty percent are based on a very few monomers. Variety in properties of these polymer compositions has been obtained through differing combinations of the monomers in simple copolymers, block and graft copolymers and in a myriad of polyblends and of composites with various fillers. Often complex and costly processes are devised to modify and improve the properties of useful compositions. For example, styrene-acrylonitrile copolymer (SAN) has desirable properties of moldability and solvent resistance but has very poor impact resistance. Acrylonitrile-butadiene-styrene terpolymers (ABS) were developed, therefore, to furnish impact resistant compositions. The ABS terpolymers of value generally are produced by forming SAN in the presence of preformed polybutadiene (PBD) to yield a graft terpolymer composition in processes much more complex than is simple terpolymerization. Even the ABS compositions have deficiencies, however, a major one being poor resistance to weathering attributable to the PBD.
Much effort has been expended to find a suitable substitute for the PBD portion of ABS. Among other candidates, rubbery ethylene-vinyl acetate (EVA) has been suggested, e.g., by Bartl and Hardt, Adv. Chem. Ser. No. 91, 477 (1969). However, SAN does not suitably graft to EVA, and only recently have desirable SAN-EVA graft compositions been prepared by the device of pre-exchanging some of the EVA acetate groups for methacrylate groups to introduce graftable unsaturation therein (Ohshima et al., Japan Pat. No. 73-01,715), or by coreacting some 5-40% of a monoolefin in a modified grafting operation as is disclosed in Alberts et al., U.S. Pat. No. 3,855,353. Such devious methods are commercially unattractive, and technology continually seeks simple and rapid methods to combine readily available compositions into more desirable ones.
When a combination of components which normally are incompatible is desired, it is now known to achieve compatibilization by adding a preformed graft copolymer in which segments represent each of the incompatible components as in Gaylord, U.S. Pat. No. 3,485,777 or to react a mixture of such materials with a coupling agent (e.g., combination of an unsaturated carboxylic anhydride and a free radical initiator) to induce in situ grafting as in Gaylord, U.S. Pat. No. 3,645,939. However, even these latter processes have disadvantages; e.g., the process of the former Gaylord patent requires special graft copolymer additives, while that of the latter requires a volatile coupling agent which offers very low efficiency in practice.
Accordingly, it is an object of this invention to provide a simple, rapid and efficient method to produce novel and useful polyblends and composites. Another object of this invention is to compatibilize normally incompatible blends and composites by inducing chemical condensation reactions between functional groups innate to the components thereof.
It is a more specific objects of this invention to compatibilize normally incompatible blends and composites of at least one nitrile group containing component with at least one other component normally incompatible therewith, but containing functional groups chemically condensable with nitrile groups, by bringing the components together in the presence of a minor amount of acid compatibilization agent. A quite specific object of this invention is to provide novel impact and age resistant polyblends of EVA in SAN through a simple, rapid and efficient process.
These and other objects of the invention will become apparent to those skilled in the art from the following detailed description.